1. Field of the Invention
The present invention relates to a silencer having an outer sleeve made of an aluminum or aluminum alloy, and is intended particularly for improvement in efficiency of the production of a silencer and improving dependability of connection of a silencer with an exhaust pipe, by improving a structure of connection of the outer sleeve with an iron or steel member.
2. Description of the Prior Art
A silencer is composed of an outer sleeve, an inner sleeve formed by a punching sheet, and acoustic material inserted between the outer sleeve and the inner sleeve. The silencer is connected with an exhaust pipe for introducing an exhaust pipe at one end of the silencer, and with a discharge pipe at the other end thereof.
In the silencer due to the lightweight of body cars and bikes to which the silencer is applied, an outer sleeve of the silencer is mostly made of aluminium. However, since the inside of the silencer is exposed to hot exhaust gas, an inner sleeve and an end cap for closing a downstream end of the inner sleeve are generally made of iron or steel.
However since aluminum or aluminum alloy cannot be welded with iron or steel connection of aluminium or an aluminum alloy with iron or steel is made by caulking or clamping with bolts. However, if connection of an outer sleeve made of an aluminum or an alluminum alloy with an end cap made of iron or steel is made only by caulking, when heat of exhaust gas is transmitted to the silencer, looseness of caulked parts is occasionally caused by differences in the coefficient of thermal expansion of aluminum or an aluminum alloy and iron or steel.
Referring to FIG. 6, a conventional silencer is illustrated. At an upstream end of a silencer shown in FIG. 6, a unit of an inner sleeve 53 made of iron or steel and an end cap 56 made of iron or steel was previously made by welding the former to the latter, and the unit is inserted into an outer sleeve 51 through acoustic material 54, and addition supplementary member 55 is attached to the unit from the outside of the unit. The peripheral portion of the supplementary member 55 is lapped in an end portion of the outer sleeve 51 and caulked together with the end portion of the outer sleeve 51, and then the supplementary member 55 is welded to the outer sleeve 51.
Further, at a connection of the silencer 50 on the upstream side with an exhaust pipe, a body 52 of castings or forgings made of aluminum is welded to the outer sleeve. The body 52 has a hole for receiving the exhaust pipe 59 at the center of the body. A plurality of tapped holes 52a are arranged around the hole for receiving the exhaust pipe. On the other hand, a flange-like mounting seat 57 also made of iron or steel is welded to the exhaust pipe 59 at the fixed position thereof. The mounting seat 57 has a plurality of bolt holes 57a at the corresponding positions to the respective tapped holes 52a. When the silencer 50 is attached to an exhaust pipe 59, first, the body 52 is engaged with the exhaust pipe 59, and steel bolts 58 are screwed into the tapped holes 52a through bolt holes 57a of the mounting seat 57.
However, in the above-mentioned structure of the conventional silencer, after the fixed inward parts have been inserted into the outer sleeve, at the last process, the end portion of the outer sleeve 51 is caulked together with the supplementary member 55 and the end cap 56. Accordingly, since caulking work for the final product is weighty and, there are problems since the apparatus for holding the outer sleeve is large sealed, and that close attention is needed to clamping and handling during production of a silencer so that the outer sleeve is not damaged or collapsed.
Further, there is a possibility that on the upstream side of the silencer due to expansion and contraction of the body 52 and the bolts 58 by driving and stopping the engine, looseness of the bolts 58 against the tapped holes 52a is caused. Accordingly, there is a dependablity on a connection of the silencer with an exhaust pipe.